OFFSET
2,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 2..200
EXAMPLE
The lowest and higest prime factors of 2^6-1 are 3 and 7, so A(6) = 21
MAPLE
a:= proc(n) local F; F:= numtheory:-factorset(2^n-1); min(F)*max(F) end proc:
seq(a(n), n=2..50); # Robert Israel, Nov 05 2014
MATHEMATICA
plhpf[n_]:=Module[{fn=FactorInteger[n]}, fn[[1, 1]]fn[[-1, 1]]]; Table[plhpf [2^n-1], {n, 2, 40}] (* Harvey P. Dale, May 23 2020 *)
PROG
(PARI) for(n=2, 50, p=2^n-1; print1(factor(p)[1, 1]*factor(p)[#factor(p)[, 1], 1], ", ")) \\ Derek Orr, Nov 05 2014
(Python)
from sympy import primefactors
A249780_list, x = [], 1
for n in range(2, 10):
....x = 2*x + 1
....p = primefactors(x)
....A249780_list.append(max(p)*min(p)) # Chai Wah Wu, Nov 05 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Jacob Vecht, Nov 05 2014
EXTENSIONS
More terms from Derek Orr, Nov 05 2014
STATUS
approved